This invention relates to a method and apparatuses for tissue imaging, especially for positioning tissue within the imaging space.
Various positioning methods are utilized for example in mammography, where it is known e.g. to compress the tissue to be imaged between compression plates and/or even to physically pull within the imaging space.
Currently, there is a multitude of known technologies used for tissue imaging, such as, for example x-ray, ultrasound, and magnetic imaging technologies. Imaging has become a proven method for the detection of e.g. cancers and other abnormalities before they advance to a phase that is difficult to treat or incurable.
One of the problem areas associated with the imaging of tissue involves the positioning and retaining of tissue within the imaging space during the imaging process. The more successful one is in positioning of the tissue within the imaging space, the less probable is the need for subsequent exposures in place for the unsuccessful ones. Problems encountered in positioning may also result in more images of a tissue area becoming taken than would be absolutely necessary. These problems are emphasized when x-rays are used, in which case the importance of radiation hygiene, i.e. the need to minimize exposure of the tissue to radiation, must always be taken into consideration.
One of the methods utilized for the positioning of tissue, especially in mammography, is compression of the tissue to be imaged. The main reason for compressing tissue is to keep it in place during the imaging process. However, when the tissue layer to be imaged gets thinner, the amount of radiation also gets smaller and the imaging time is shortened, which further reduces the inaccuracies caused by movement of the tissue under exposure. Furthermore, as a result of a thinner layer of tissue the contrast of the image improves as scattering is reduced, which simultaneously enables the use of lower imaging values (kV). Additionally, resolution improves, the film darkens more homogeneously, and the result is a diagnostically more valuable image, since possible deviations of superimposed tissue layers are more effectively differentiated from each other.
In mammography, areas easily excluded from the imaging space are those close to the chest wall and armpits, where cancers and tissue abnormalities quite often occur. On the other hand, the process of compression can even lead to part of the tissue under exposure being pushed out of the imaging space. Therefore, efforts have been made in this field to develop various solutions related to compression plates and compression methods that would make it possible to pull or otherwise manipulate the tissue of the chest and breast areas in such a fashion that the imaging space created by the compression plates would retain as much tissue as possible. Even negative pressure has been used in an attempt to draw tissue into the imaging space by suction.
A rather new and interesting method for drawing the breast into the imaging space has been presented in U.S. Pat. publication No. 5,553,111. According to this procedure, a layer of radiolucent material is positioned between the compression plate and the tissue to be imaged, for instance a layer of plastic film. This film is positioned between the tissue to be imaged and the contact or compression surfaces of the compression plates, for example so that the film passes both over and under the breast. Thereafter, the film is pulled in the direction of the tip of the breast in order to pull more tissue within the imaging space. The publication proposes utilizing either one continuous layer of film to pull tissue from opposite sides, or separate bands of film that are fastened at both ends to their individual film conveyors in order to create substantially a ring-shaped stretching means, which passes around the compression paddle used for compressing the tissue to be imaged.
In principle, the technology described in U.S. Pat. publication No. 5,553,111 contains many advantageous features. However, in a practical application of these principles the solutions presented are in many respects problematic. Because. of the modern demand for strict hygiene, among other things, it would be advisable to change the disposable film or the corresponding stretching means for every client. The solutions specified in the patent publication for pulling the film, and for fastening it to the traction device, etc., do not include a means for quickly changing the stretching means between customers. In addition, in the solutions presented, sanitizing the traction device in situ would be awkward and uncertain. For example, in mammography screening tests, the time factor is of such importance that it would appear that the technology described in the publication could not be utilized as such, except possibly for clinical imaging.
Therefore, the object of the invention presented here is to raise the level of technology in the field of positioning methods related to tissue imaging.
Specifically, the object of the invention presented herein is to develop the technology based on tissue stretching means so as to speed up the practical process of imaging.
The object of the invention is to provide a solution whereby the tissue stretching means could be simply, quickly and easily fed and fastened to a tissue pulling device, thereby resulting in a reduction of the total imaging time and eliminating difficult installation procedures.
The object of the invention is to provide a solution to feeding the stretching means into the traction device in such a way that a sheet-like stretching means, or stretching means of some other, in its principal dimensions essentially a rectangular configuration, could be fed into the traction device as easily as a bank card or a note is fed into an. automatic cash dispenser, or the like.
The object of the invention is also to provide a solution for fastening the tissue-stretching means to the tissue-stretching device so as to guarantee a rapid, secure and non-slip lockage of the stretching means to the traction device.
Moreover, the aim of the invention is to provide such a solution for fastening the stretching means to the traction device, as well as to provide such a traction device, that the stretching means can be both pulled into the device as well as driven out of it.
The object of the invention is also to provide an imaging system that utilizes tissue traction technology whereby the imaging methods and imaging sequences typically used in mammography can be applied simply, efficiently and, if so desired, to some degree automatically.
The aim of the invention is also to enable the utilization of all those components generally used in mammography, such as the various compression paddles, image information receivers, grids, etc., in the same fashion as before.